The Number of and the Strength of Tropical Storms is Not Increasing.

Bill's Blog

The aCE Index – a measure of the number and strength of torpical storms.

The graph above from Dr. Ryan Maue ( shows 12-month running summaries of the number of tropical storms and hurricanes (also knows as typhoons in the Western Pacific and cyclones in the Indian Ocean and around Australia). The graph shows that there has been very little change over the past 50 years in the number of tropical storms and hurricanes. Dr. Maue writes: ” There is no significant trend in the number of global tropical storms and/or hurricanes since 1970.”

2019 global tropical cyclone summary: 87 tropical storms, including 48 of hurricane strength. 31 reached major strength (Cat 3+). There were 4 Category 5 hurricanes, with Hurricane Dorian (160-knots) the strongest (over Grand Bahama and Abaco Islands of the Bahamas. (Preliminary as final intensity analysis will occur in next 6-months).

Summary by decade: 2010s: 826 global tropical storms, 445 became hurricane strength, 249 majors (Cat 3+) 2000s: 855 global tropical storms, 450 reached hurricane strength and of those, 248 majors (Cat 3+) 1990s: 256 majors (Cat 3+) Very similar numbers.

Eastern Pacific ACE Indes 1981 – 2014

This is a graph from the NOAA that shows the ACE Index from 1981-2014 for the Eastern Pacific (east of the International Date Line). Note that they divide the “High Activity Era” – pre-1995 from the “Low Activity Era” – after 1995. Again, this is only for the Eastern Pacific.

Here’s a link to the ACE Index from 1970-2016 from The ACE Index is a measure of the number of and the intensity of tropical storms and hurricanes in the Atlantic. Note the decrease in the 10 years following 2005 – the year we had Hurricanes Katrina, Rita and Wilma.

Here’s a link to a graph of the global ACE Index from 1970 – 2019. The graph has a 24-month running sum. to better observe any trend. The 1990s appears to be the decade with the highest overall ACE Index.

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